Wavelength selective coatings for optical disc security

Abstract

An optical disc for data storage includes a layer of color-shifting material. Light passing through the color-shifting layer will have a color determined by the various constructive and destructive interference of the various wavelengths after they have passed through the material, diffracted while passing through the material, and are reflected off of various portions of the material, resulting in a color change when the viewing angle is changed. Additionally, an optical variable device may be defined within the disc, and may include the color-shifting layer.

1. An optical disc for storage of digital data, the optical disc comprising:
 a transparent base having an optically flat side and an imprinted side, the imprinted side having a plurality of indentations defining the data; 
 the reflective layer disposed on the imprinted side; 
 the optical disc defining an optically flat data side from which the data may be read, and a label side opposite the data side; and 
 a color shifting layer including one or more layers of color shifting material, including at least one layer of liquid crystal material, the color shifting layer being disposed in a location selected from the group consisting of the reflective layer, a location viewable from the label side of the disc, and a location spatially separated from the data that is viewable from the data side of the disc. 
 
   
   
     2. The optical disc according to  claim 1 , wherein the liquid crystal material is a cholesteric liquid crystal material. 
   
   
     3. The optical disc according to  claim 1 , wherein each layer within the color shifting coating is a liquid crystal material. 
   
   
     4. The optical disc according to  claim 3 , wherein the color shifting layers includes a first layer of liquid crystal material orientated in a first direction. 
   
   
     5. The optical disc according to  claim 4 , wherein the color shifting layer includes a second layer of liquid crystal material, orientated in a second direction. 
   
   
     6. The optical disc according to  claim 5 , wherein the first layer and second layer are made from liquid crystal materials having a different combination of liquid crystal monomers. 
   
   
     7. The optical disc according to  claim 1 , further comprising an optical variable device structured to be viewed from a location selected from the group consisting of the label side of the disc and a location within the data side of the disc spatially separated from the label side of the disc. 
   
   
     8. The optical disc according to  claim 7 :
 further comprising a protective coating over the color-shifting layer; and 
 wherein the optical variable device is formed within the transparent protective coating. 
 
   
   
     9. The optical disc according to  claim 8 , wherein each layer within the color shifting coating is a liquid crystal material. 
   
   
     10. The optical disc according to  claim 9 , wherein the color shifting layers includes a first layer of liquid crystal material orientated in a first direction. 
   
   
     11. The optical disc according to  claim 10 , wherein the color shifting layer includes a second layer of liquid crystal material, orientated in a second direction. 
   
   
     12. The optical disc according to  claim 11 , wherein the first layer and second layer are made from liquid crystal materials having a different combination of liquid crystal monomers. 
   
   
     13. The optical disc according to  claim 7 , wherein the color-shifting layer is deposited onto the optical variable device. 
   
   
     14. The optical disc according to  claim 13 , wherein each layer within the color shifting coating is a liquid crystal material. 
   
   
     15. The optical disc according to  claim 14 , wherein the color shifting layers includes a first layer of liquid crystal material orientated in a first direction. 
   
   
     16. The optical disc according to  claim 15 , wherein the color shifting layer includes a second layer of liquid crystal material, orientated in a second direction. 
   
   
     17. The optical disc according to  claim 16 , wherein the first layer and second layer are made from liquid crystal materials having a different combination of liquid crystal monomers. 
   
   
     18. The optical disc according to  claim 7 , wherein the optical variable device is selected from the group consisting of a hologram, a diffraction grating, and a holographic diffraction grating. 
   
   
     19. The optical disc according to  claim 7 , wherein the optical variable device is formed within a second transparent base within the optical disc. 
   
   
     20. The optical disc according to  claim 1 , wherein the optical disc is a digital versatile disc, having an opaque color-shifting layer and a semitransparent color-shifting layer. 
   
   
     21. The optical disc according to  claim 20 , wherein the opaque color-shifting layer is a color-shifting layer. 
   
   
     22. The optical disc according to  claim 21 , wherein each layer within the color shifting coating is a liquid crystal material. 
   
   
     23. The optical disc according to  claim 22 , wherein the color shifting layers includes a first layer of liquid crystal material orientated in a first direction. 
   
   
     24. The optical disc according to  claim 23 , wherein the color shifting layer includes a second layer of liquid crystal material, orientated in a second direction. 
   
   
     25. The optical disc according to  claim 24 , wherein the first layer and second layer are made from liquid crystal materials having a different combination of liquid crystal monomers. 
   
   
     26. A method of making an optical disc, the optical disc defining a data side from which the data may be read, and a label side opposite the data side, the method comprising:
 providing a transparent base having an optically flat side and a data side, the data side having a plurality of indentations defining the data; and 
 providing a reflective layer covering the data side; and 
 providing a color-shifting layer comprising one or more layers of color shifting material, including at least one layer of liquid crystal, the color shifting layer being disposed in a location selected from the group consisting of the reflective layer, a location viewable from the label side of the disc, and a location spatially separated from the data that is viewable from the data side of the disc. 
 
   
   
     27. The method according to  claim 26 , wherein the step of providing a color shifting coating includes the step of depositing a layer of liquid crystal material. 
   
   
     28. The method according to  claim 27 , wherein the step of providing a color shifting coating is performed by a process selected from the group consisting of silk screening, slot coating, gravure coating, reverse gravure coating, and flexography. 
   
   
     29. The method according to  claim 27 , wherein the step of providing a color shifting coating includes providing a second layer of liquid crystal material, the first layer orientated in a first direction, and the second layer orientated in a second direction. 
   
   
     30. The method according to  claim 29 , wherein each of the layers of liquid crystal material comprises a different combination of liquid crystal monomers. 
   
   
     31. The method according to  claim 26 , further comprising providing an optical variable device spatially separated from the data. 
   
   
     32. The method according to  claim 31 , wherein the optical variable device is formed by providing a protective layer, and embossing the optical variable device within the protective layer. 
   
   
     33. The method according to  claim 32 , further comprising:
 depositing a color-shifting coating on the optical variable device; and 
 covering the optical variable device with a transparent protective coating. 
 
   
   
     34. The method according to  claim 31 , wherein the optical variable device is formed by providing a second transparent base having the optical variable device thereon, and securing) the optical variable device to the label side of the transparent base having the data. 
   
   
     35. The method according to  claim 34 , further comprising:
 depositing a color-shifting coating on the optical variable device; and 
 covering the optical variable device with a transparent protective coating. 
 
   
   
     36. The method according to  claim 26 , wherein the liquid crystal material is deposited by a process selected from the group consisting of silk screening, slot coating, gravure coat, gravure coagravure coating, and flexography. 
   
   
     37. The method according to  claim 26 , wherein the step of providing a color shifting coating over the optical variable device includes depositing a second layer of liquid crystal material upon the first layer of liquid crystal material, the first layer of liquid crystal material having a first orientation, and the second layer of liquid crystal material having a second orientation. 
   
   
     38. The method according to  claim 37 , wherein each of the layers of liquid crystal material includes a different combination of liquid crystal monomers.